http://tainguyenso.vnu.edu.vn/jspui/handle/123456789/12060 2026-05-17T17:57:11Z 2026-05-17T17:57:11Z Dang Thanh, Trung et al. http://tainguyenso.vnu.edu.vn/jspui/handle/123456789/14146 2011-08-09T03:20:22Z 2011-08-09T00:00:00Z

The single moving dipole source for electrocardiography inverse problem in 3D human model Dang Thanh, Trung; et al. Computing electrical source in the heart from potentials on the body surface is an ill-posed problem of electrocardiogram (ECG). It is so difficult to get an exact solution of this problem. To solve this ECG inverse problem, a numerical analysis is used for forward problem with a specific source model. Then, the solutions of ECG inverse problem is reached by using an iterative technique, Newton or downhill simplex, to find the best source whose potentials best match to the observed potentials in a least square sense. Such methods, however, often converge to a local minimum and their results are affected by initial parameters. In this paper, source is considered as a moving single equivalent dipole and genetic algorithm, an efficient and robust optimization method, is proposed to estimate parameters of source. In addition, some improvements are introduced to enhance performance of conventional genetic algorithm. A 3D volume conductor model of human body is constructed base on an anatomic atlas for numerical test. A comparison between our approach and one using downhill simplex method is implemented. The results show that our approach is stable and may provide a good scheme for solving the ECG inverse problem.

2011-08-09T00:00:00Z Nguyen Huu, Mui Vu Dinh, Hoa http://tainguyenso.vnu.edu.vn/jspui/handle/123456789/14145 2011-08-09T03:16:19Z 2011-08-09T00:00:00Z

Active schedules and a new hybrid genetic algorithm for the job shop scheduling problem Nguyen Huu, Mui; Vu Dinh, Hoa Active schedules and a new genetic algorithm for solving job shop scheduling problem are presented in this paper. In the proposed method, a chromosome representation of the problem is natural numbers, the GT algorithm is used to generate a set of active solutions, the mutation is implemented on the all machines concurrently. Especially, we propose a new crossover operator that combines the uniform crossover operator with GT algorithm and is implemented on 3 parents. The approach was tested on a set of benchmark programs and compared with other approaches. The computation results validated the effectiveness of the proposed algorithm.

2011-08-09T00:00:00Z Le Thi Mai, Oanh et al. http://tainguyenso.vnu.edu.vn/jspui/handle/123456789/14144 2011-08-09T03:13:39Z 2011-08-09T00:00:00Z

Classification of natural tourmalines using near-infrared absorption spectroscopy Le Thi Mai, Oanh; et al. Six natural tourmaline crystals with different colors were investigated by near-infrared (NIR) absorption spectroscopy. The tourmaline crystals were obtained from Lucyen mines in Vietnam. The NIR absorption spectra were recorded in two ranges of 4000-5000 cm-1 and 6500- 8000 cm-1 . We found, according to their NIR spectra features, these six tourmaline crystals can be classified into four groups: G1, liddicoatite; G2, elbaite; G3, dravite; and G4, Uvite. This grouping is consistent with the chemical composition analyses and our earlier Raman studies.

2011-08-09T00:00:00Z Nguyen Nang, Dinh et al. http://tainguyenso.vnu.edu.vn/jspui/handle/123456789/14143 2011-08-09T03:11:04Z 2011-08-09T00:00:00Z

Thermochromic properties of VO2 films made by RF-sputtering Nguyen Nang, Dinh; et al. Vanadium dioxide films with nano-structured grains have been prepared by RF- sputtering followed by thermal annealing in low oxygen pressure. The submicro-structured crystalline grains with the size of 200 to 250 nm were revealed by FE-SEM micrographs. XRD analysis proves the monoclinic lattice of the VO2 crystalline structure and the size of the grains determined from XRD also consists of about 200 nm. The temperature of the semicoductor-to- metal phase transition (SMPT) of the films was found at tc = 64 o C. At temperatures higher than tc the resistance of the films decreased three orders in magnitude, and the transmittance at l = 1550 nm lowered from 55% to a value as low as 30%. From these thermochromic properties of VO2 films one can suggest a practical application in production of thermo-optical sensors that can be used for monitoring temperature change in petrol and/or toxic chemical storages.

2011-08-09T00:00:00Z